Field of the Invention
The present invention refers to a device for monitoring tyres for vehicle wheels.
The invention further refers to a tyre for vehicle wheels provided with said monitoring device.
The invention refers also to a method for installing an electronic unit in a tyre for vehicle wheels.
Description of the Related Art
For some types of tyres, above all the ones for which high-level performances are required, monitoring devices have been studied for a long time that, being mounted inside said tyres, will have the function of detecting characteristic quantities of the tyre, in order to allow a control of the functioning and of the conditions of the tyre itself substantially in real time.
Such monitoring devices will periodically communicate with the instruments available on board of the vehicle, so that all the relevant information will be provided to the driver and/or to control systems of the vehicle, for example for activating or for regulating at best warning systems and/or controlling systems of the vehicle, of the braking, etc.
The monitoring devices for tyres typically comprise an electronic unit and a connection element. The electronic unit comprises at least one sensor, for example a temperature sensor, a pressure sensor, a sensor able to measure/identify the deformations undergone by the tyre while rolling, such as for example an accelerometer, a strain gauge, etc., and a transmission system for sending the data detected by said at least one sensor.
The connection element has the function of keeping the electronic unit constrained to the tyre. In particular, in order to identify and to measure the deformations undergone by the tyre and to estimate, from said deformations, some parameters (e.g. the Length of the tyre footprint, the load weighing on the tyre, the angular speed, the friction between the tyre and the rolling surface, the wear of the tyre, etc.), it may be convenient to have one or more monitoring devices in correspondence of the crown portion of the tyre, namely the one placed in correspondence of the tread hand of the tyre itself. In particular, it may be convenient to arrange one or more monitoring devices on the inner surface of the tyre, for example on the portion of inner surface opposite to the tread band.
A fundamental problem of the connection elements relates to the fact that the tyre, above all at the beginning and at the end of the tyre footprint area, undergoes mechanical stresses which provoke relevant deformations. On the other hand, the case which houses the electronic unit is typically made of a substantially rigid material, in order to protect its content and to allow a correct functioning of the electronic unit itself.
The fact that the electronic unit (rigid) should be constrained to the inner surface of the tyre (that undergoes deformation) is a very critical aspect for the connection element: the latter, although being secured to the inner surface of the tyre, and thus being subject to the same stresses as the tyre, has to keep a reliable and durable constraint with a substantially non-deformable object, namely the case of the electronic unit.
The Applicant verified that, in case the connection element is not properly structured, the exchange of stresses between the case of the electronic unit and the connection element may bring to tears and/or breakings of the connection element itself, up to release the electronic unit from the tyre. Such tears may also have microscopic dimensions, initially, and then progressively expand up to compromise the structural integrity of the connection element. The electronic unit, after the breaking of the connection element, will be then free to move inside the tyre during the rolling of the tyre itself, with consequent problems for a correct detection and transmission of the data, and with the risk of breakings and/or failures of the electronic unit itself.
Such problem was faced and solved by the monitoring devices described in the patent applications WO2010/043264, WO2006/103706, WO2007/000781, WO2007/121768, WO2013/098711, WO2013/098712 in the name of the same Applicant.
The shape of the connection elements used in such monitoring devices allows to obtain a mechanical decoupling between the electronic unit and the deformations undergone by the inner surface of the tyre, thus providing a reliable and durable constraint.
With more detail, such connection elements have two separate base surfaces intended to be connected to the inner surface of the tyres so that the mechanical stresses undergone by the tyre are absorbed by the connection element, also by virtue of the fact that the two base surfaces can be deformed/moved in a substantially mutually independent way, thus following the deformations of the inner surface of the tyre. Only a small part of such deformations/stresses are thus transmitted to the electronic unit, thereby significantly reducing the risk that the rigidness of the case may damage the connection element.
The Applicant, however, noticed that this type of connection elements cannot be effectively used for particular categories of sensors, which indeed have the function to detect the stresses and the deformations undergone by the tyre, particularly in correspondence of the tyre footprint area.
Such sensors, indeed, may be adapted to detect data useful to identify particular operating conditions/situations, such as for example the friction between the tyre and the road surface, the forces exchanged in the tyre footprint area, the evolution of the shape of the tyre footprint area, the wear of the tyre, an aquaplaning condition, etc., that are determined based on the analysis of the mechanical stresses in tangential, longitudinal and/or radial direction undergone by the tyre.
By way of example, it is possible to consider the processing techniques described in the patent applications WO2005/005950, WO2005/043106, WO2005/042281, WO2005/042322, WO2006/034731, WO2007/102175, WO2008/065465, WO2010/046872, WO2010/046871, WO2010/073272, WO2012/042369, WO2012/085649, WO2012/085655, in the name of the same Applicant.